This invention relates to a drawer type enclosed switchboard equipped with an automatic grounding device.
Heretofore, a drawer type enclosed switchboard has not been equipped with any grounding device.
The conventional drawer type enclosed switchboard without grounding members is constructed of a switchboard proper 1, and has an outer truck device 26 which is held in engagement with the switchboard proper 1, and an inner truck device 34 which moves horizontally inside the outer truck device 26 and which has main circuit equipment built therein. An operating lever 48 for panel operations is disposed in a manner to penetrate through a faceplate 28 at the front surface of the outer truck device 26, and an operating circular lever 47 and an operating mechanism-rotary shaft 46, which are directly connected to the operating lever 48, are received in an operating box 32, whereby a rotary operating mechanism is constructed. A rotary arm 49 is attached to the operating mechanism-rotary shaft 46, and is provided with a guide pin 50 for operating the inner truck. Further, the guide pin 50 is held in engagement with a guide rail slot 45 which is formed in a guide seat 44 provided at the front surface of the inner truck. Owing to the above state of engagement, the operation of rotating the operating lever 48 is converted into a horizontal motion on the basis of the relationship of engagement between the rotary arm 49 for operating the inner truck and the guide rail slot 45 of the inner truck, whereby the movement of the inner truck and the operation of disconnecting a main electric circuit become possible.
Since the conventional drawer type enclosed switchboard is constructed as described above, the load side circuit of the main circuit needs to be grounded separately from the above arrangement in order to prevent an accident due to electric shock when the switchboard is inspected during maintenance. Accordingly, in the enclosed switchboard which has the primary disconnecting portion of the automatic connection type on the truck device, it has been necessary that, after the truck portion has been drawn out of the switchboard, a load side terminal of each phase is grounded by means of a ground rod at the rear of the switchboard, or that a grounding operation is performed by providing a separate grounding device of a truck type into the switchboard instead of the truck.
Such grounding operations in the prior art have had the disadvantage that a long time is required for the operations. Further, in the case of employing the grounding device separate from the truck device, the truck portion must be completely removed out of the switchboard in order to execute the grounding operation, and hence, the inspection area becomes small. Moreover, in a case where the grounding operation is performed for a large number of switchboards, the grounding device is shared, so that the time required for a service interruption becomes long and a safe operation of maintenance inspection cannot be efficiently performed. In addition, since the grounding device is an accessory component separate from the truck device, it is demeritorious in cost, as well as requiring a custody space when not being used.